JPS6142408A - Determination of finish pass schedule - Google Patents

Abstract

PURPOSE:To maintain the crown on an outlet side in addition to the sheet thickness and temp. on the outlet side at target values with a smaller quantity of calculation in a title method for a tandem rolling installation provided with a function for shifting work rolls by maintaining and processing the crown of each stand within a permissible value. CONSTITUTION:The predicted crown or crown ratio C on the outlet side of each roll in the standard pass schedule (expressed as standard PS) for which load distribution and work roll shift are applied is determined. The permissible max. and min. crowns to be determined from the shape change of the (n-1)th stand are determined when the C on the outlet side of the final n-th stand is different from the target value. The C of the (n-1)th stand in the standard PS is so changed as to be kept within the above- described range by a min. of change when said C is out of the permissible range and the similar change of C is executed successively up to the initial stand. The change of the C is executed by changing the quantity S of the above-mentioned shift and when the change of the C is within the capacity of the quantity S, the above-described PS is adopted simply by subjecting the same to the above-described change to the quantity S. When there is the stand of which the C exceeds the capacity of the quantity S as a result of the change, the loading load of such stand is also changed and the above- described PS is subjected to the change to the quantity S and the rolling load and is then adopted.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention not only ensures a target plate thickness and temperature on the finished exit side in a tandem rolling equipment having a work roll shift function, but also provides a good shape on the exit side of each stand. The present invention relates to a method for determining a bus schedule that achieves a five-finished mountain side target crown while maintaining the same.

(Prior art) The conventional method for determining the rolling schedule is generally to distribute the power and load required for rolling according to the capacity of each rolling mill, and the crown and shape of the rolled plate are not considered. Not done.

In addition, in recent years, a technique has been reported in which the reduction schedule is changed between the first half and the second half of the schedule in order to suppress variations in the strip crown within the rolling schedule, but even in this case, changes in the strip crown that are expected in advance for a specific rolling schedule In order to deal with this, the change pattern of the rolling reduction schedule is simply given in advance, and the rolling schedule is determined by considering the factors that affect the plate crown shape in setting subtraction for each rolled material. Therefore, it has the disadvantage that it is difficult to apply it to operations where the organization of rolling schedules changes significantly, which has been the trend in recent years.

[Problem that the invention seeks to solve]

The present invention provides a 4n +
The purpose is to solve the problems of the conventional method using rolling equipment such as a mill, and in addition to setting the exit side plate thickness and temperature generally required for hot rolling to target values, This paper attempts to provide a method for determining the path (crown) schedule.

It has been considered to control the crown by changing the reduction distribution, but the conventional method is to increase the load on the front stage of the tandem rolling mill group to make the crown smaller, or increase the load on the latter stage to make the crown larger. Therefore, it is not possible to perform sophisticated round control such as keeping the crown of each stand within the allowable value and setting the final stage crown to the target value in order to suppress deterioration of the shape.

The DP method (Dynamic Programming) is used to search for Hit iM values such as determining bus schedules.
g method: For example, open door, lead powder [bus schedule optimization theory and rolling operation evaluation function] (Plasticity and processing, vo
l. 9No88 (196B) 315-323))
is effective, but it requires a huge number of calculations and can only be used if the computer has sufficient capacity. Therefore,
It is also an object of the present invention to enable an easy search for an optimal value.

c) Means for Solving Problems) The present invention provides a bus schedule that ensures the target plate thickness and temperature on the finished exit side, maintains the exit side shape of each stand well, and achieves the target crown on the finished exit side. In the determination method,
Calculate the expected crown or crown ratio at the exit side of each stand under the standard bus schedule with load distribution and work roll shift applied, and if the expected crown or crown ratio at the exit side of the nth final stand differs from the target value, calculate the expected crown or crown ratio at the exit side of the final stand. Find the allowable maximum crown and allowable minimum crown determined from the shape change of the previous n-1st stand, and the expected crown or crown ratio of the n-1st stand in the standard bus schedule does not fall within the allowable range. If so, change the expected crown or crown ratio so that it falls within the allowable range with the minimum change, and sequentially change the expected crown or crown ratio up to the first stage stand, and change the crown based on the shift amount of the work roll. If the change in the expected crown ratio up to the first stage is within the capacity of the work roll shift amount, the bus schedule is adopted only by making the change to the work roll shift amount,
If a stand exceeds the work roll shift capacity due to changes in the expected crown or crown ratio up to the first stage, the rolling load of the stand will also be changed and the bus schedule will be adapted to the work roll shift amount and rolling load. Although the present invention is characterized in that it is adopted with some modifications, its structure and operation will be described in detail below with reference to the drawings.

〔Example〕

Figure 1 shows an overview of the crown set-up model. When the inlet side plate thickness, outlet side plate thickness, etc. of the tandem rolling equipment are given, the plate thickness at the outlet side of each stand is calculated from these. From this calculated plate thickness on the outlet side of each stand, the rolling load P of each stand
i (i=1, 2...), and then calculate the plasticity curve gradient aP i /δ■(.Next, each stand outlet plate crown Ci is calculated by the following formula.

C4= (] −ηi) Ci+ηi (1−ri)
(, -H...(1) C1=Cp-Pl+Cs-3iCfFi+CROH...
...(2) Here, C is the uniform load plate crown, η is the crown ratio genetic coefficient, r is the rolling reduction ratio, Cp, Cf and O3 are the rolling load P,
The influence coefficient of roll bending force F and work roll shift ls on the crown, CRO is the influence coefficient on the roll profile crown, Ci is the shape change coefficient, Δε
indicates the exit shape quantitatively by the strain difference.

The crown has genetics from the previous stand.

The second term in equation (1) indicates this, and the i-stand exit crown ratio has η1(] for the front stage exit crown C1-1.
-ri) is included. y7i-
There is a relationship of C11nr+C2r+C3,r=D2uh2/B2. Here, 01 to C3 are constants, D is the work roll diameter, h is the exit side plate thickness, and B is the plate width. The first term in equation (1) indicates that the product of the crown C, which occurs when the load is uniform, that is, the load distribution in the plate width direction is uniform, multiplied by (1-η) appears on the exit side crown. , the actual plate crown is the sum of both.

As expressed by equation (2), the uniform load plate crown (Ci is the rolling load Pi10 - the pending force Fl.

It is determined by the roll shift amount Si and the roll profile CRO. C/H is the crown ratio, and the change in shape is proportional to the difference between the crown ratio of the i-stand and the crown ratio of the 1-1 stand (on the entry side when viewed from the i-stand). This is equation (3). The shape change coefficient ξi is ξi−1/(1
+a Iy+a 2 y2). Here 2
+, a2 are constants.

To calculate the crown, hi, P as shown in the curve
i and Fi must be determined, and as for hi, that is, the plate thickness, the inlet and outlet thicknesses of the tandem rolling equipment are given, but the outlet side thickness of the intermediate stand can be set to various values within a range that does not cause problems. Possible.

FIG. 4 is a diagram showing this, where the horizontal axis is the pass (stand) number and the line axis is the exit side plate thickness. One value is the Oth
Pass, that is, rough exit side plate thickness and 7 passes (Jul final pass) 1] 1 side plate thickness, intermediate 1 to 6 stunt exit side plate thicknesses take appropriate values within the range of ear wave limit and medium elongation limit La, Lb. obtain.

Therefore, it can be said that there are an infinite number of combinations of old IL + board thickness for each stand, and in the DP method, for each of these combinations, (1)
~ Calculate formula (3) and find an appropriate round Ci,
This requires enormous calculations. Therefore, in the present invention, the second
Adopt the method shown in the figure.

In FIG. 2, the explanation will be made using the crown ratio, but FS is the standard schedule curve of the crown ratio, which connects the exit crown ratios of each stand when the standard bus schedule is adopted. The standard bus schedule is set according to the load distribution of each stand, roll change, work roll shift amount, etc. determined based on experience, taking into consideration root connectivity, equipment capacity, etc., and the curve FS is the standard bus schedule creation method. The standard load distribution, standard work roll bending capacity, work roll shift amount, etc. are determined from the standard table (consisting of a table showing the percentage value of the load assigned to each stand by steel type, plate width, plate thickness, etc.) used in The above fll (obtained by calculating 61゛ using formula 21, etc.)
A curve FS is obtained by calculating j from 1-1 to 7, and it is checked whether the final stand exit crown ratio C7p matches the target crown ratio C7a. In this example this is a mismatch, C7a > C7p. C7a? C
If it is 7p, it must be changed so that C7a = C7p, but if you simply do this, the crown change ΔC at the No. 7 stand becomes ΔC - C7a - C6p, which means that Δε in equation (3) above becomes excessive. There is a risk that it will happen.

If the target crown ratio of the No. 7 (final) stand is 07a, the allowable values of the exit side crown ratio (herein simply referred to as crown) of the No. 6 stand are maximum C62 and minimum C61. In other words, the crown on stand No. 6 is the target crown C7a.
If the size is smaller, it is necessary to control the size of the crown for the No. 7 stand, and if this control is performed too strongly, it will cause ear waves, so there is a minimum value that does not cause this ear wave generation, and the second
In the figure, this is designated as C61. Similarly, if the crown of the No. 6 stand is larger than the target crown Cia, it is necessary to control the crown of the No. 7 stand to make it smaller, and if this is done forcefully, it will cause elongation, so this will not occur. There is a maximum value, which is C62 in FIG. Therefore, if the target crown is C7a, the allowable value for the crown of the No. 6 stand is C61 or more and G62 or less. In this example, the crown predicted value cap of stand No. 6 is not within the above range, so it is necessary to change the CI)p.In the present invention, this change is made with the smallest amount of change (standard schedule curve FS (as much as possible). Therefore, in this example, C61' is changed to Cal.

If the crown of the sixth stand is C61, for the same reason as above, the crown of the fifth scum l- also has an allowable maximum value and an allowable minimum value, and in this example, these are assumed to be C52 and C51. Since the predicted crown value csp of the fifth stand is not within this allowable range, the above process is performed here as well, and Cap is changed to C51. The same applies below, or -
The process is carried out up to the first stand.

Crown changes are made by adjusting the roll shift NSi. Crown change amount ΔCi (i=1.2...7)
is the crown of each stand adopted as above.
As ia, ΔCi = C1a-Cip, which is F
If it is realized by i, it is from the above fl) (formula 21).

Roll shift l-1si + ΔSi force required to change the Cip of each stand to Cia (If it is within the capacity of the work roll shift amount, rolling can be executed with this (with the bus schedule where only shift 1 ~ amount is changed), so the next step is the rolling reduction value is calculated, and the setting calculation is completed.If the above required work roll shift amount exceeds the capacity of the shift], it is impossible to change the crown by work roll shift alone, and in this case, the rolling load is also The amount of change in rolling load is determined by calculating ΔCI' from the amount of crown change ΔC1' of the stand, and
From equation (2) above, it is obtained as ΔPi - ΔCi/Cpi. Here, ΔCi′=C1a−C4p′, and Cip
' is the i-stand exit crown after changing only the shift amount. That is, ΔCi is slightly corrected by changing the work roll shift amount, and the remaining ΔC1' is corrected by the load. If the rolling load changes, the plate thickness will change, so we need to correct it. The original plate thickness (-positive quantity ΔHi is calculated as follows. The denominator on the right side of this equation (4) is called the plasticity curve slope and represents the hardness of the material.

FIG. 3 is an explanatory diagram of a rolling mill having a work roll shift device, where S is a rolled material, WR is a work roll, SS is a shift device thereof, RB is a hending device, and BUR is a hack-up roll.

5 and 6 show the results of implementing the crown control of the present invention. The vertical axis in FIG. 5 is the plate crown, the horizontal axis is the rolling order (number of coils), the vertical axis in FIG. 6 is the actual crown, and the horizontal axis is the calculated crown. As shown in the figure, the calculated value and the measured value of the plate crown are in good agreement with an accuracy of 5±20μ.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to achieve the target finishing crown while satisfying the shape of each stand, and the calculations required for this are the initial calculation of the standard IjtFS, the subsequent calculation of the correction of the work roll shift amount, If that is not enough, you only need to calculate the subsequent modification of the rolling load.
This has the advantage of requiring less calculation. Therefore, according to the present invention, the plate thickness accuracy is improved by improving the head crown setting accuracy, which greatly contributes to improving the yield.

[Brief explanation of the drawing]

Fig. 1 is a flowchart explaining the present invention, Fig. 2 is a detailed explanatory drawing of the invention, Fig. 3 is an explanatory drawing of a rolling mill with a large crown control function having a work roll shift device, and Fig. 4 is a bus Explanatory diagram of schedule calculation, Figures 5 and 6
The figure is an explanatory diagram of a comparison between calculated values and actual values. In the drawing, C5p, Cap, CHI), Cip is the expected crown ratio of each stand under the standard bus schedule, and C6
2, C112 is the maximum allowable crown, Cat. C5+ is the minimum allowable crown.

Claims (1)

[Scope of Claim] A method for determining a bus schedule that achieves a target crown on the finished exit side while ensuring the target plate thickness and temperature on the finishing exit side and maintaining the exit shape of each stand well, comprising: Calculate the expected crown or crown ratio at the exit side of each stand in the standard bus schedule with roll shift applied, and if the expected crown or crown ratio at the exit side of the n-th final stand differs from the target value, calculate the expected crown or crown ratio at the exit side of the n-th final stand. The allowable maximum crown and allowable minimum crown determined from the shape change of the n-1st stand are determined, and if the expected crown or crown ratio of the n-1st stand in the standard bus schedule does not fall within the allowable range, the minimum allowable crown is calculated. The expected crown or crown ratio is changed so that the change falls within the allowable range, the expected crown or crown ratio is sequentially changed up to the first stage stand, and the crown change is performed by changing the shift amount of the work roll, If the change in the expected crown ratio up to the first stage is within the capacity of the work roll shift amount, the bus schedule is adopted with only the change made to the work roll shift amount, and the expected crown or crown ratio up to the first stage is changed. If a stand exceeds the capacity of the work roll shift amount due to the change, the rolling load of the stand is also changed, and the bus schedule is adopted with the change made to the work roll shift amount and rolling load. How to determine the final bus schedule.